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Can I initialize an object using the constructor of another class?

Can I initialize an object using the constructor of another class?

class1 object = new class2();
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As long as it class2

extends (or implements in the case of an interface) class1

, that's fine. For example,List<String> list = new ArrayList<>();



To be clear, you are instantiating class2

(or ArrayList

from my example). It just so happens that you have specified your type variable class1

(or List

).

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The only way to work in C ++

class1 object1 = new class2();

will have an implicit conversion between class2*

and class1

. This can be achieved with a conversion constructor:

struct class1
{
  class1(const class2*);
};

Whether or not it uses the constructor of a class to "help" to create an object of another, it depends on what you mean by helping build.



If you meant

class1 object1 = class2();

then the conversion constructor must take a value class2

by value or reference. For example,

struct class1
{
  class1(const class2&);
};

There is no need for an is-a relationship between types.

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C ++ only: Possibly, but classes require a polymorphic "is" relationship (public inheritance in C ++). For example:

class class1 { };
class class2 : public class1
{
    class2(int) {}
};


class1* object1 = new class2(42); // A pointer is needed (in C++)
delete object1;

// better would be:
std::unique_ptr<class1> object1(new class2(42));

Edit: In the meantime, the thread developer has removed the C ++ - Tag, so my answer has nothing to do with it anymore.

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This is only possible if class2 is a subclass of class 1. This is called polymorphism.

class Class1{
 /*
  *
  *
  body of class1
  *
  */
 }


class Class2 extends Class1{
 /*
  *
  *
  body of class2
  *
  */
 }

Then you can declare

Class1 object1 = new Class2 ();

Hope this helped.

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class class1{}
class class2 extends class1{}

If you have parent relationships with children in a class hierarchy, this is not a problem. then   class1 object1 = new class2();

what actually happens internally is you have a class2 object, but it is referenced by the class1 variable.

but if you have

class class1{}
class class2{}

Then it doesn't work

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